3-Methylene cephalosporins

ABSTRACT

3-Methylene cephalosporins and their salts and esters which are useful as intermediates in the preparation of antibiotics. The title compounds are prepared by the reduction of a 3carbamoyloxymethyl- or 3-acetoxymethyl cephalosporin.

United States Patent Ponticello et al.

S-METHYLENE CEPHALOSPORINS Inventors: Gerald S. Ponticello, BridgewaterTownship, Somerville County; F. Edward Roberts, Princeton; Leonard M.Weinstock, Belle Mead, all of NJ.

Assignee: Merck & Co., Inc., Rahway, NJ.

Filed: May 15, 1972 Appl. No.: 253,221

U.S. Cl. 260/243 C; 424/246 Int. Cl C07d 99/24 Field of Search 260/243 CReferences Cited UNITED STATES PATENTS 12/1970 Long et al 260/243 C 1May 13, 1975 3,660.396 5/1972 Wright 260/243 C 1705.897 l2/l972Murphy... 260/243 C 3 [6,465 2/l973 Heusler et al r 4. 260/243 C3,733.320 5/l973 Pines et al 260/243 C Primary ExaminerNicholas S. RizzoAuomey, Agent, or FirmWalter Patton; Julian S. Levitt; J. Jerome Behan 3Claims, No Drawings 1 3-METHYLENE CEPHALOSPORINS This invention isdirected to novel cephalosporin compounds having a S-methylenesubstituent and also to a novel process for preparing said compounds.

The 3-methylene cephalosporins and their salts and esters are useful asintermediates to prepare cephalosporin antibiotics.

The cephalosporin compounds prepared from the novel products of thisinvention are effective against gram-negative bacteria includingEscherichia (o/i, Pmteus vulgaris, Proteus mirabilis, Proteus morganii,salmonella scholtnme/l'eri, Klebsiella pneumoniae AD, Klebsiellapneumoniae B, and Paracolobaclrum arizoniae and gram-positive bacteriaincluding Staphylocoo cus aureus, Streptococcus pyogener and Diplucoccuspneumoniae.

The cephalosporins prepared from these novel intermediates are alsouseful in removing susceptible microorganisms from pharmaceutical,medical and dental equipment and as bactericides in industrialapplications, for example, in water based paints and in the white waterof paper mills to inhibit the growth of harmful bacteria.

The novel compounds of this invention have the following structuralformula:

wherein R is an acyl radical, for example, an aliphatic aromatic,heterocyclic, araliphatic or heteroeyclic aliphatic carboxylic acidradical of the formula;

R is hydrogen or a a blocking group and Y is hydrogen or an organicradical, for example, any radical presently known in the cephalosporinart which is stable under the reaction conditions employed. Examples ofthese radicals are hydroxy or substituted hydroxy groups; a hydrocarbylor substituted hydrocarbyl group; cyano or a carbonyl containingsubstituent or a nitrogen bonded group.

The following list is an illustration of the various Y radicals whichcan be employed; however, the list is not meant to be exhaustive for, asmentioned previously, any known cephalosporin having a 3-acetoxymethylor 3-carbamoyloxymethyl radical maybe employed in this reaction, theonly limitation being that the Y function be stable to the reactionconditions employed.

Y can be a radical of the formula: OY wherein Y is straight or branchedchain lower alkyl of l-6 carbon atoms, preferably methyl or ethyl, loweralkenyl of 3-6 carbon atoms, lower alkynyl of 3-6 carbon atoms,monocyclic aryl such as phenyl or a monocyclic aralkyl such as benzyl.When Y is hydrocarbyl, it can be lower alkyl of l-6 carbon atoms, loweralkenyl of 36 carbon atoms, lower alkynyl of 36 carbon atoms, monocyeliearalkyl, cycloalkyl of 56 carbon atoms or a monocyclic aryl group. whenY is a carbonyl substituent, it has the formula:

l la wherein Y is hydroxy, amino, substituted amino, lower alkyl or l6carbon atoms and the like and the nontoxic pharmacologically acceptablesalts thereof.

Those compounds wherein Y is methoxy and the acyl radical, R, is of theformula:

wherein R and R are as defined below, represent a preferred group ofradicals because of the generally enhanced antibiotic activity of the A"cephem compounds containing these radicals. R represents hydrogen, halo,amino, hydroxy, tetrazolyl or carboxy. R represents phenyl, substitutedphenyl, a 5 or 6-membered monocyclic heterocycle containing one or moreoxygen, sulfur or nitrogen hetero atoms in the ring such as fury],thienyl, thiazolyl, isothiazolyl, oxadiazolyl and the like, substitutedheterocycles, phenylthio, hcterocyclic or substituted heterocyelic thiogroups or cyano. The sub stituents can be halo, carboxymethyl,aminomethyl, methoxy or methyl. Expecially preferred are those acylradicals Where R is hydrogen, amino or carboxy and R is phenyl or a 5-or fi-membered heterocyclic ring containing from l to 2 sulfur, oxygenor nitrogen atoms. Examples of these preferred R radicals arephenylacetyl, 3-bromophenylacetyl, p-aminomethylphenylacetyl,4-carboxymethylphenylacetyl, 2-furylacetyl, 3- furylacetyl,5-chlorothienylacetyl, S-methoxythicnyla- Cetyl, 3-thienylacetyl,4-methylthienylacctyl, 3- isothiazolylacetyl,4-methoxyisothiazolylacetyl, 4- isothiazolylacetyl,3-methylisothiazolylacetyl, 5-

isothiazolylacetyl. 3-chloroisothiazolylacetyl, 4-acetyl,phenylthioacetyl, 4-pyridylthioacetyl, cyanoacetyl, tet razolylacetyl,a-fluorophenylacetyl, Dmhenylglycyl, 4-hydroxy-D-phenylglycyl,Z-thienylglycyl 3- thienylglycyl, phenylmalonyl, 3-chlorophenylmalonyl,2-thienylmalonyl, 3-thienylmalonyl, a-hydroxyphenylacetyl anda-tetrazolylphenylacetyl. An especially preferred substituent is2-thienylacetyl.

The novel process of this invention comprises treating a3-carbamoyloxymethylor 3-acetoxymethyl-7B-acylamido-7a-(Y-substitutedl-3-cephem-4-carboxylic acid ester with areducing agent. for example, activated zinc dust or zinc dust in thepresence of formic acid. [The zinc is activated by washing it withdilute hydro chloric acid, removing any trace of hydrochloric acid andthen drying the zinc dust under vacuum.] Any solvent which is inert orsubstantially inert to the reactants may be employed with the activatedfor example, tetrahydrofuran, ethyl acetate, dioxane, acetic acid andthe like. When a solvent other than acetic acid is employed, it has beenfound desirable to add a small amount of acetic acid (up to 10% byvolume) to increase the yields. The reaction may be conducted at atemperature in the range of from about 0 to 50C. ln general the reactionis conducted at ambient temperature. The reaction time is generally fromabout 10 min utes to about 60 minutes. The following equationillustrates this reaction:

ester function, care should be taken to chose those groups which willnot be cleaved.

wherein R, R and Y are as defined above and R is acetoxy orcarbamoyloxy.

ln carrying out this reaction the 4-carboxy group and other carboxy,amino or hydroxy groups in the nucleus are preferably protected with anester group (R in the formulas), for example, an ester group selectedfrom trichloroethyl, tert-butyl, benzoylmethyl, pmethoxybenzyl, benzyl,benzhydryl, trimethylsilyl, methoxymethyl, benzoylmethylcarbonyloxy,tertbutylcarbonyloxy and the like. These ester groups may be removed byvarious methods, for example, the benzhydryl or phenylalkyl may beremoved by hydrogenation in the presence of a catalyst such aspalladium-oncarbon or by treatment with a strong organic or inorganicacid. The tert-butyl or methoxymethyl groups may also be removed bytreatment with a strong organic or inorganic acid. Examples of theseacids are hydrochloric acid, sulfuric acid, boron trifluoride etherate,formic acid, trifluoroacetic acid, trichloroacetic acid, nitrobenzoicacid and the like.

Under the reaction conditions employed some of the abovementioned estergroups may be cleaved to afford the free acid. Therefore, if it isdesired to retain the The 3-methylene cephalosporins are useful as intermediates in the preparation of other cephalosporins having antibioticactivity or in the preparation of the desirable 3-bromomethylsubstituted cephalosporin which can be reacted with a nucleophilicsubstance to obtain a 3-functionalized methyl cephalosporin product.Numerous examples of the nucleophilic substances which can be employedare already known in the art.

The 3-substituted methyl cephalosporins (Ill, infra) are prepared bytreating the 3-methy1ene cephalosporin (l, infra) with a reagent whichadds across the double bond of the S-methylene group, for example,halogens such as bromine and the like or haloazides such as bromineazide and the like. This reaction is conducted under free radicalconditions employing polar solvents such as chloroform, methylenechloride and the like. The 3-halo-3-substituted methyl cephalosporins(IV, infra) are treated with a weak base such as collidine, sodiumacetate, calcium oxide, dimethylformamide and the like to afford thedesired 3-substituted methyl cephalosporin (Ill). The following equationillustrates this process:

r ENE-{ 9 CH X 1-1 2 halo 1 2 1 -OR ill-OR \LBase Y RNl-L- S 0 N ca xwherein R, R and Y are as defined above and X is halo such as bromo andthe like or azido.

lncludcd within the scope of this invention are the salts of the instantproducts. In general. any base which will form a salt with the3-methylene cephalosporins is considered as being within the scope ofthis invention, for example. salts prepared from alkali metal andalkaline earth metal bases.

Also included in addition to the esters described above are other esterderivatives which are prepared by conventional methods. These includethe lower alkyl esters such as methyl ester, ethyl ester and the like.

These salts and esters of 3-methylene-7B-acylomido-7a-(Y-substituted)-cepham-4-carboxylic acid are considered to be thefunctional equivalent of the corresponding acid.

The 3-carbamoyloxymethyl and 3-acetoxymethyl cephalosporins (ll)employed as starting materials in this invention are disclosed inBelgian Pat. No. 768,528.

The following examples illustrate the novel process of this invention.However, the examples are illustrative only and it will be apparent tothose skilled in the art that other reagents and solvents similar tothose described in the following examples may be employed to affordsimilar results.

EXAMPLE 1 3-Methylene-7B-thienylacetamido-7amethoxycepham-4-carb0xylicAcid Step A: Methoxymethyl3-methylene-7B-thienylacetamido-7a-methoxycepharn-4-carboxylate To asolution of methoxymethylcarbamoyloxymethyl-7B-thienylacetamido-7amethoxy-3-cephem-4-carboxylate(40 mg.) in tetrahydrofuran (4ml.) containing acetic acid (0.2 ml.) isadded activated zinc dust (1.8 g.) [zinc dust is activated by washingseveral times with 5% hydrochloric acid, and then washing successivelywith water, methanol and then ether and finally drying the zinc dustunder vacuum.] The reaction mixture is stirred at room temperature forminutes. The reaction mixture is filtered and the zinc cake washed withtetrahydrofuran. The solvent is removed under vacuum and the residuedissolved in ethyl acetate and washed with a 5% sodium bicarbonatesolution. The ethyl acetate solution is dried over magnesium sulfate,filtered and the ethyl acetate removed under vacuum to affordmethoxymethyl3-methyeIne-7B-thienylacetamido-7ameethoxycepham-4-carboxylate.

Mass Spectrum: (M 412; UV: )tmax 270 A% 24', )tmax 232 A%211;

NMR (CDCl (5.61-1, 3.43 ppm OCH (S, 2H, 3.9 ppm m (m, 3H, 7.1 ppm all(S, [H m 7.65 ppm N-li).

Step B: 3-Methylene-7B-thienylacetamidoJoz-methoxy cepham-4-carb0xylicAcid (S, 1H, 5.15 ppm C -H): (m, 3H, 5.25 ppm Ii-C-CO H); (S. 1H, 9.43ppm EXAMPLE 23-methylene-7B-thienylacetamido-7amethoxycephem-4-carboxylic Acid To asolution of 3-carbamoyloxymethyl-7B-thienylacetamido-7amethoxy-3-cephem-4-carboxylic acid mg.) intetrahydrofuran (10 ml.) containing acetic acid (lml.) is addedactivated zinc (1.8 g.). The reaction mixture is stirred overnight atroom temperature. The reaction mixture is filtered and the zinc cakewashed with tetrahydrofuran. The solvent is removed from the filtrateunder vacuum to afford a mixture of the starting material and finalproduct. The mixture is triturated with dry ethyl acetate in which thedesired product is soluble and the starting material is insoluble. Theethyl acetate solution is filtered and the solvent removed under vacuumto afford 3-methylene-7B- thienylacetamido-7a-methoxycephem-4-carboxylicacid. Further purification of the product is done on preparative thinlayer chromatography using as the solvent system a mixture of benzene.methanol and acetic acid in a ratio of 50:10:05.

EXAMPLE 3 Methoxymethyl3-Melboxymethylbromomethyl-7B-thienylacetamido-7a-methoxy-3-cephem-4-carboxylateMethoxymethyl 3-methylene-7-thienylacetamido-7-methoxycepham-4-carboxylate is dissolved in methylene chloride l ml.)and cooled to 0C. To this solu tion is added bromine (1 mm.) inmethylene chloride (l0 ml.). After 30 minutes at 0C. the solvent isremoved under vacuum to afford methoxymethyl 3bromomethyl-3-bromo-7-thienylacetamido-7- methoxycepharn4-carboxylatc.This compound is dissolved in dimethylformamide (l0 ml.) and sodiumacetate (1 mm.) is then added. The reaction mixture is heated to 60C.for 4 hours. The reaction mixture is diluted with ethyl acetate (100ml.) and is washed with water to remove the dimethylformamide. Thesolution is concentrated under vacuum to afford Methoxymethyl3-bromomethyl 7B-thienylacetamido-7amethoxy-3-cephem-4-carboxylate.

EXAMPLE 4 3-Azidomethy1-7,B thienylacetamido-7a-methoxy-3-cephem-4-carboxylic Acid Step A: Methoxymethyl3-azidomethyl-3-bromo-7-thienylacetomido-7- methoxycepham4-carboxylateMethoxymethyl 3-methylene-7B-thienylacetamido-7a-methoxycephem-4-carboxylated (1 mm.) is dissolved in methylenechloride 10 ml.) and treated with a solution of bromine azide l mm.) inmethylene chloride 10 ml. After the disappearance of the red color thesolvent is removed under vacuum to afford methoxymethyl3-azidomethyl-3-bromo-7-thienylacetamido- 7-methoxycepham-4-carboxylate.

Step B: Methoxymethyl 3 azidomethyl-7B-thienylacetomido-7a-methoxy-3-cephem-4-carboxylate Methoxymethyl 3-azidomethyl-3-bromo-7-thienylacetamido-7-methoxycepham-4-carboxylate is dissolved indimethylformamide (10 ml.) and sodium acetate (4mm) is added. Thesolution is heated at C. for 1 hour and then diluted with ethyl acetate(50 ml.). The solution is washed with water to remove thedimethylformamide. The solution is then concentrated under vacuum toafford methoxymethyl 3-azidomethyl-7B-thienylacetamido-7a-methoxy-3-cephem-4- carboxylate.

Step C: 3-Azidomethyl-7B-thieeylacetamido-7ameth0xy-3-cephem-4-carboxylic Acid Methoxymethyl 3-azidodmethyl-7B-thienylacetamido-7a-methoxy-3-cephem-4- carobyxlate is dissolved indimethylformamide l0 ml.) and methanol (2 ml.) and concentratedhydrochloric acid (2Ml.) i added at 0C. The reaction mixture is allowedto stand for minutes at 0 to 5C. at which time a sodium bicarbonatesolution (2.5 g.) in water (25 ml.) is added. The alkaline solution iswashed with ethyl acetate and the ethyl acetate solution is discarded.The solution is then cooled to 0C. and layered over with ethyl acetatel5 ml.). The pH is adjusted to 2 with 10% hydrochloric aicd.d The ethylacetate solution is collected, dried over magnesium sulfate, filteredand the solvent removed over vacuum to afford 3azidomethyl-7B-thienylacetamido-7a-methoxy-3- cephem-4-carboxylic acid.

UV: )tmax. 263 A% 200 IR: (B-lactam C=O) 1775 cm.

(N 2100 cm- By following substantially the procedures described inExamples 1-4, all of the products of this invention may be prepared. Thefollowing equation, together with Table 1, indicate the startingmaterials, intermediates and products which may be prepared by thisprocess:

Y RNH- S -'N 4 r? la a E-OR RNHi-fl-f Y RNH--I H N Br (f Br 1 OR1 'r A BL E 1 (continued) Ex l 4 No. R n R Y o o 37 1L 1.!

G CHCH3 o m-x ii 38 @cac- CH i1 2 L02}! 3 L n 9 411 cn ocn occH What isclaimed is:

l. A compound of the formula:

wherein R is furyl or thienyl; and X is halo or azido.

2. A compound according to claim I named methoxymethyl3-methylene-7B-thienylacetamido-7a methoxycepham-4-carboxylate.

3. A compound according to claim I named mcthoxymethyl3-methyIene-7B-furylacetamido-7amcthoxycepham-4-carboxylate.

1. A COMPOUND OF THE FORMULA:
 2. A compound according to claim 1 namedmethoxymethyl 3-methylene-7 Beta -thienylacetamido-7 Alpha-methoxycepham-4-carboxylate.
 3. A compound according to claim 1 namedmethoxymethyl 3-methylene-7 Beta -furylacetamido-7 Alpha-methoxycepham-4-carboxylate.